Existing encoders may be used in automatic utility meter reading or any application where total flow must be monitored at remote locations over long time periods. They can be included in any device that utilizes rotating wheels to measure cumulative flow of gas or liquid. In these meters, the total number of rotations of the wheels is indicative of the total flow through the meter. Common encoders involving optical, electrical contacts, or inductive mechanisms may be used. Absolute rotary encoders are a subset of rotary encoders, which provide information about the rotational position of each reel at any time, without the need to monitor and count pulses caused by the movement of the wheel. These encoders typically include a rotating wheel and provide an appropriate output of the wheel position. Although there are many possible ways of counting, each wheel's rotation typically represents 10 digits, for example, the encoder wheel can be numbered from 0 to 9. In addition to electronic output, these encoders also may provide visual readings. A common encoder is configured with at least one wheel, if the recording time is long such that several decades of counting is needed, more wheels are necessary. In these multi-wheel arrangements, the first wheel of a pair turns one full rotation, causing the second wheel to turn 0.1 rotations, although a different ratio may be used. Within a multi-wheel meter, generally except for the first wheel, one full rotation of the preceding wheel N will cause the successive N+1 wheel to rotate 0.1 turns. This multi-wheel assembly configured as such can therefore record readings over several decades.
Other encoder technologies are known in the art such as: optical transmission, optical reflectance, electrical contact. Optical methods suffer from problems from dirt and light pollution, and high expense due to needed electronic components for both light source and light detector. Electrical contact encoders suffer from low reliability as they wear out over time. Other magnetic encoder technologies are known in the art such as magnetic targets with alternating magnetizations, and inductive detectors. Magnetic targets are more expensive; their physical precision is limited by the ability to impress a permanent magnetization on the material.
To overcome these shortcomings an improved invention with lower cost, simpler design, and magnetic disks with greater precision will be useful to the flow metering industry.